Even in a case where a rapid variance is demanded as to the input voltage of a converter and the output terminal voltage of a fuel cell, stable converter control is realized. On judging that the change ratio of the demand power of a fuel cell exceeds a set threshold value, a controller executes converter stabilization processing. First, the controller controls a battery converter so that an input voltage of an inverter becomes a set target input voltage. Then, after the input voltage of the inverter reaches the target input voltage, the controller controls an FC converter so that an output terminal voltage of the fuel cell becomes a set target output terminal voltage.